Problem: Solve for $k$. $ \dfrac{9}{10} = \dfrac{10}{k} $ $k =$
Multiply both sides by ${k}$. $ {k} \times \dfrac{9}{10} = \dfrac{10}{k} \times {k} $ $ \dfrac{9}{10}{k} = 10 $ Multiply both sides by ${\dfrac{10}{9}}$. $ \dfrac{9}{10} {k} \times {\dfrac{10}{9}} = 10 \times {\dfrac{10}{9}} $ $ {k} = \dfrac{10 \times {10}}{{9}} $ $k = \dfrac{100}{9}$